CVE-2026-98277: eth: fbnic: ring the doorbell if a burst ends in a drop

CVE-2026-98277: eth: fbnic: ring the doorbell if a burst ends in a drop

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

eth: fbnic: ring the doorbell if a burst ends in a drop

fbnic_tx_map() skips the doorbell write, and the completion request,
for every packet handed to it with xmit_more set, counting on the
packet which ends the burst to publish them all. When that packet is
dropped instead - skb_put_padto(), skb_cow_head() or a DMA mapping
failure - nothing rings. The descriptors of the preceding packets stay
invisible to the HW until the next transmit on that queue, which for a
burst-then-idle workload may never come.

Remember the meta descriptor of the last packet left without a doorbell
and flush it from the error paths. The completion request has to be set
on that descriptor rather than simply writing the tail, otherwise the HW
would transmit the packets but never report a head, and the ring would
fill up and stall for good.

This is very similar to Joe's recent series of fixes for bnxt.
Not seen in real life, reproduced under QEMU with failure injection.

The Linux kernel CVE team has assigned CVE-2026-98277 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.11 with commit 9a57bacd574b52b08bc2c600af6a8c7a87049ecf and fixed in 6.18.54 with commit 60ef74357a36ed2a102a75bb68d37aa7f305b94e
	Issue introduced in 6.11 with commit 9a57bacd574b52b08bc2c600af6a8c7a87049ecf and fixed in 7.2.8 with commit 28fb764d670aa22dcbd2a02fd8fd87ae8d3563a9
	Issue introduced in 6.11 with commit 9a57bacd574b52b08bc2c600af6a8c7a87049ecf and fixed in 7.3-rc4 with commit 490599ab23134962a6d18a024e84541d77bdb999

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-98277
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/net/ethernet/meta/fbnic/fbnic_txrx.c
	drivers/net/ethernet/meta/fbnic/fbnic_txrx.h


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/60ef74357a36ed2a102a75bb68d37aa7f305b94e
	https://git.kernel.org/stable/c/28fb764d670aa22dcbd2a02fd8fd87ae8d3563a9
	https://git.kernel.org/stable/c/490599ab23134962a6d18a024e84541d77bdb999